DE 197 31 369 C1 discloses a generic air-conditioning unit for a motor vehicle having a fan and an evaporator, wherein a bypass channel bypassing the evaporator is provided.
DE 10 2010 029 495 A1 discloses a further generic air-conditioning unit.
CN 201205858 Y and JP 2006027377 A disclose air-conditioning units.
To enable the efficiency of today's air-conditioning units to be maximized, the aim is to only use as much energy for cooling and for heating in the air-conditioning unit as is actually needed for achieving or preserving the climatic comfort in the vehicle cabin. Avoiding unnecessary energy for cooling and for heating has a negative impact on the operating range, in particular in electric vehicles.
Modern air-conditioning units having regulated, externally controllable refrigerant compressors or electric refrigerant compressors enable the temperature level of air expelled at the exit of an evaporator to be raised up to ca. 12° C. If higher blow-out temperatures are required at the outlets of the air-conditioning unit depending on the ambient temperatures and the climate control of the vehicle interior, the air has to be additionally supplied with heat by way of the heat exchanger arranged in the air-conditioning unit. This frequently occurring operating situation is typical here for maintaining a state of comfort in the vehicle cabin and is thus a determining factor for the efficiency.
To keep the heating energy used for this as low as possible, the prior art discloses so-called bypass channels which bypass the respective evaporator of the air-conditioning unit on one side and thereby raise the temperature level. However, the bypass channels disclosed in the prior art are disadvantageous here in that the airflows exiting the evaporator and the bypass channel do not mix sufficiently with one another, which can result not only in undesired temperature strands and thus impairments to comfort but, in the worst case, also in a stratified airflow and a steaming-up of the windscreen, which can also impair the driving safety. Moreover, an unfavourable and, in particular, also non-reproducible mixing of the airflow from the evaporator and the bypass channel hinders the adjustment of the air-conditioning unit to achieve reproducible continuous regulating curves.